This invention relates to an improved process for the recovery of phosphate values from phosphatic-mineral-containing materials; and more particularly relates to chemically leaching phosphate values from any phosphatic-mineral containing material with a novel mixture leach acid.
Production of phosphorus-containing products is a long established and commercially important industry and with the demand rapidly rising, especially in the production of food for the growing world population, phosphorus becomes increasingly more important to the overall world need. Thus there is a need for an improved process for the treatment of phosphatic materials, and more particularly to the selective extraction and concentration of phosphate values from a wide range of phosphatic materials, including besides rock, as-mined phosphate ores and phosphatic waste materials regardless of contaminating chemical and mineral impurities such as iron oxide, aluminum oxide, silica, clay, etc. or their quantity in the phosphatic mineral source.
Prior processes for the production of most phosphate products require phosphate rock. Phosphate rock for phosphate processes must be relatively free of sand, slimes, and iron oxide, aluminum oxide, and any other impurity that chemically interferes with the solubilizing and separation of phosphate. Also, rock must have removed from it those minerals which interfere with the chemical processing operations such as filtration, crystallization, solubilization, etc.
The operations of converting phosphate ore to phosphate rock are costly and produce adverse environmental conditions. Besides contamination of the surrounding area with silts, the removal of slimes (iron minerals, aluminum minerals, and other fines) produces large slime ponds which take years to eliminate. Further, processing losses of phosphate values for rock production can be as much as 40 percent. In addition many sources of phosphatic materials cannot be so processed.
The processing of phosphate rock whether by the wet method, that is present day chemical extraction, or the furnace method will also produce problems of contaminating the surrounding environment unless extensive and costly provisions are made to contain the obnoxious chemicals.
While there are patents which may deal with a dilute acid alone they have a number of deficiencies. British Pat. No. 938,468 and published Dutch application No. 700,258 allude to some attempt to utilize a dilute acid in a wet method but such require inter alia either great insufficiencies or excesses of acid quantity; overstepping or under-stepping multiple additions to stationary leaching vessels; and obtaining monocalcium phosphate leach liquors. In addition, investigation indicates these processes never achieved any degree of commercial acceptance.
This invention both eliminates the need for the production of phosphate rock and its adverse affects such as slime ponds, etc., and also the obnoxious chemical contamination produced by the processing of rock to phosphate products in a commercially feasible process.